Crystal structures of three 4-substituted-2,2′-bipyridines synthesized by Sonogashira and Suzuki–Miyaura cross-coupling reactions

Facile synthetic routes for three 4-substituted 2,2′-bi­pyridine derivatives, 4-[2-(4-methyl­phenyl)­ethyn­yl]-2,2′-bi­pyridine, C(19)H(14)N(2), (I), 4-[2-(pyridin-3-yl)ethyn­yl]-2,2′-bi­pyridine, C(17)H(11)N(3), (II), and 4-(indol-4-yl)-2,2′-bi­pyridine, C(18)H(13)N(3), (III), via Sonogashira and Suzuki–Miyaura cross-coupling reactions, respect­ively, are described. As indicated by X-ray analysis, the 2,2′-bi­pyridine core, the ethyl­ene linkage and the substituents of (I) and (II) are almost planar [dihedral angles between the two ring systems: 8.98 (5) and 9.90 (6)° for the two mol­ecules of (I) in the asymmetric unit and 2.66 (14)° for (II)], allowing π-conjugation. On the contrary, in (III), the indole substituent ring is rotated significantly out of the bi­pyridine plane [dihedral angle = 55.82 (3)°], due to steric hindrance. The crystal packings of (I) and (II) are dominated by π–π inter­actions, resulting in layers of mol­ecules parallel to (30-2) in (I) and columns of mol­ecules along the a axis in (II). The packing of (III) exhibits zigzag chains of mol­ecules along the c axis inter­acting through N—H⋯N hydrogen bonds and π–π inter­actions. The contributions of unknown disordered solvent mol­ecules to the diffraction intensities in (II) were removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9–18] algorithm of PLATON. The given chemical formula and other crystal data do not take into account these solvent mol­ecules.